How do I make sudo stop sending me useless emails?

This problem is caused by sudo looking for directives in a place it cannot find them: sss.
Check the /etc/nsswitch.conf file and modify the sudoers entry.

sudoers: files sss

The sss should not be there. The sssd-ad package adds itself there, but very few environments store sudoers directives in sss. It’s far more likely your directives are local, so you should have a /etc/nsswitch file entry like the following: